*{
    padding: 0;
    margin: 0;
    list-style: none;
}
.box{
    width: 300px;
    margin: 0 auto;
}
.active{
    background: blue;
}
.ul li{
    width: 300px;
    height: 300px;
    border: 1px solid red;
    text-align: center;
    line-height: 300px;
    font-size: 30px;
    display: none;
} 
.ul .show{
    display: block;
}
